Generation of coherent broadband photon pulses with a cascaded longitudinal space-charge amplifier
A. Marinelli, E. Hemsing, M. Dunning, D. Xiang, S. Weathersby, F. O’Shea, I. Gadjev, C. Hast, and J. B. Rosenzweig
Accepted
The longitudinal space-charge amplifier has been recently proposed as an alternative to the free electron laser instability for the generation of intense broad-band radiation pulses (\textit{Phys. Rev. ST Accel. Beams 13, 110701 (2010)}). In this Letter we report on the experimental demonstration of a cascaded longitudinal space-charge amplifier at optical wavelengths. Although seeded by electron beam shot-noise, the strong compression of the electron beam along the three amplification stages leads to emission of coherent undulator radiation pulse exhibiting a single spectral spike and a single transverse mode. The on-axis gain is estimated to exceed four orders of magnitude with respect to spontaneous emission.